Improving quality of metal-contaminated soils by some halophyte and non-halophyte forage plants

Abstract

Toxic elements cause degradation in agricultural land quality. Phytoremediation of polluted sites is the safest technique to sustain ecosystem. Field trial was established to examine the performance of two Atriplex species (A. numularia and A. amnicola) and two traditional forage plants (pearl millet and cowpea) cultivated on polluted sandy soil and clean one. The studied contaminated soil was irrigated with untreated sewage wastewater for more than 60 years and contained Zn, Cu, Pb and Cd levels excessed the permissible limits. The growth of Atriplex plants was not affected by the soil pollution, while the traditional forage plants lost 40–50% of their biomass. The roots biomass of Atriplex plants was higher by 54% than those of cowpea and pearl millet plants. The crude protein (CP) and chlorophyll in the tested species were reduced as a result of soil pollution, but the reduction was higher in pearl millet and cowpea than Atriplex plants. CP in Atriplex plants that were grown in the contaminated soil was reduced by 10%, while in the case of pearl millet and cowpea; the reduction was more than 20%. Atriplex plants were more effective in reducing the metal bioavailability than pearl millet and cowpea. Atriplex plants were able to protect the photosynthesis process in the presence of toxic elements; moreover, they produced some substances that increasing the resistance of toxic metal stress such as proline. The cultivation of metal-contaminated soil with Atriplex plants enhanced the soil quality and increased the aggregation and porosity of soil; besides, it reduced the soil salinity and concentration of toxic elements. Cultivation of halophyte and traditional fodder plants in contaminated lands is a good strategic management of the ecosystem, and the resulting plant may be used to feed animals due to their low content of pollutants or be recycled to soil organic amendments.